共查询到20条相似文献，搜索用时 31 毫秒
1.
柴油发动机富氧燃烧理论分析 总被引：5，自引：0，他引：5
对柴油发动机的燃烧过程进行分析,建立燃烧的热化学动力学模型。通过对燃料燃烧的放热效率及燃烧生成物进行分析,进而对柴油发动机富氧燃烧的可行性进行理论分析。 相似文献
2.
We believe that methanol is the most versatile synthetic fuel available and its use could stretch or eventually substitute for, the disappearing reserves of low-cost petroleum resources. Methanol could be used now as a means for marketing economically the natural gas that is otherwise going to waste in remote locations. If methanol were used as an additive to gasoline at a rate of 5 to 15 percent, for use in internal combustion engines, there would be an immediate reduction in atmospheric pollution, there would be less need for lead in fuel, and automobile performance would be improved. With increasing production of fuel-grade methanol from coal and other sources, we foresee the increasing use of methanol for electrical power plants, for heating, and for other fuel applications. We hope that a practical methanol fuel cell will be commercially available by the time that methanol becomes plentiful for fuel purposes. Methanol offers a particularly attractive form of solar-energy conservation, since agricultural and forest waste products can be used as the starting material. Indeed, at 1 percent conversion efficiency the forest lands could supply the entire present energy requirements of the United States. 相似文献
3.
中高速内燃机气缸直径和活塞行程的最优设计 总被引：1，自引：0，他引：1
通过对中高速内燃机气缸直径和活塞行程的取值分析。建立了以中高速内燃机气缸直径和活塞行程为设计变量、以最小散热面积为目标函数的优化数学模型,并用模拟退火（ＳＡ）算法对实例求出最佳缸径比。以利于提高中高速内燃机的效率。可供类似设计参考。 相似文献
4.
Lakes may be acid because of natural ecological conditions or because of anthropogenic activities. Apparently there has been a recent increase in acidity of many lakes in the northeastern United States. Factors that may be contributing to this increase include the use by utilities of precipitators, sulfur scrubbers, and tall stacks; the use of petroleum; and methods of combustion of fossil fuels. 相似文献
5.
Carbon dioxide builds up in the eartht's atmosphere principally from increased use of fossil fuels. Estimates of the escalating uses of fossil fuels in the United States, especially for the generation of electric power and in the internal combustion engine, show that by the year 2000 emissions will have increased approximately eighteenfold from 1890. In the period 1965 to 1985 an emission-rate increase of around 4.0 percent per year compounded is expected. The expected intrusion and expansion of nuclear power will tend to lower the rates of increase of emission after 1985. Increases in emission rates in the rest of the world will probably equal or exceed the values projected for the United States. 相似文献
6.
Producer gas engines could have an important role in the decentralized production of mechanical energy in rural areas of less-developed countries. With this technology mechanical energy is produced from solid fuels by use of internal combustion engines. A comparison with other renewable energy options, on the common basis of energy efficiency and economics, shows that producer gas engines may have significant advantages and deserve serious attention. 相似文献
7.
对20世纪80年代美国的“排日风潮”以及美国要求日元升值对日本经济产生的影响和日本政府采取的对策进行了深入分析。针对中国目前所面临的状况,提出中国应采取的措施包括：加速产业结构调整,提高产品竞争力;努力扩大内需,减少外贸依存度;进一步完善国内金融市场;促进人民币有序升值。 相似文献
8.
Fertility in the United States 总被引：1，自引：0，他引：1
C F Westoff 《Science (New York, N.Y.)》1986,234(4776):554-559
From the postwar high of 3.8 births per woman at the peak of the baby boom, the total fertility rate in the United States has fallen to 1.8, where it has remained unchanged for nearly a decade. This below-replacement level of fertility has, in recent decades, characterized most Western countries, some of which have shown declines to well below 1.5 births per woman. Were it not for the continued infusion of immigrants, the U.S. population, which already shows the aging characteristic of low fertility, would stop growing and begin to decline before the middle of the next century. The low fertility in the United States has been accomplished by a postponement of marriage and by the widespread use of contraception, with heavy reliance on surgical sterilization as a contraceptive method. Judging from the experience of other Western countries and from our own historical experience of two centuries of fertility decline interrupted only by the baby boom, as well as from the absence of social trends that would counteract those contributing to that decline, the prognosis is for a continued low level of fertility in the United States. 相似文献
9.
本文提出一种方法新、操作方便的内燃机技术状态智能化测量系统，它使用声传感器拾取内燃机发出的噪声，用ＦＦＴ求得频谱，对ＦＦＴ算法中的误差进行了理论分析，提出了修正的方法，分析了频谱的特点，进行了信息提取、归一，给出了Ｆｕｚｚｙ模型，给出了一种用ＴｕｒｂｏＣ语言表达内燃机技术状态的具体方法，用以上方法对内燃机发出的噪声进行现场采样和分析，可以正确判断２４种内燃机的工况。 相似文献
10.
Katz RN 《Science (New York, N.Y.)》1980,208(4446):841-847
The unique properties of ceramics based on silicon carbide and silicon nitride make them prime candidates for use in advanced energy conversion systems. These compounds are the bases for broad families of engineering materials, whose properties are reviewed. The relationships between processing, microstructure, and properties are discussed. A review and assessment of recent progress in the use of these materials in high-temperature engineering systems, and vehicular engines in particular, is presented. 相似文献
11.
Koenig R 《Science (New York, N.Y.)》2000,290(5496):1484-1487
Two decades after Iran's Islamic revolution, science in this politically isolated but oil-rich nation may be on the verge of resurgence. The nation's reform-minded president, Mohammad Khatami, and his allies are promising more money for R&D, reorganizing universities to beef up graduate education and research, and cracking open the door to closer cooperation with scientists abroad, including those in the United States. But Iran's government is walking a tightrope between hard-liners on the right who oppose reforms and liberal university students eager for change. 相似文献
12.
Fundamental investigations of the chemical and physical properties of metal beta-diketonate complexes have revealed unusual volatility, as well as solvolytic and thermal stability and solubility in organic solvents. Certain general rules describing the volatility of metal beta-diketonates on the basis of ligand shell character and metal ion size have arisen from extensive gas chromatographic and vapor pressure studies. Several practical applications of volatile beta-diketonates teke advantage of their special properties. In ultratrace metal analysis by gas chromatography, use of these chelates has allowed the detection of smaller amounts of certain metals than can be detected by any other analytic method. Certain rare earth beta-diketonates have been found useful as antiknock additives in gasoline and as catalysts for the removal of carbonaceous deposits from the combustion chambers of internal combustion engines. 相似文献
13.
李东红 《农业图书情报学刊》2010,22(8):88-90,103
针对我国图书馆在门户网站建设方面的实践和国外目前已启动的数字图书馆项目,如美国国会图书馆、网络图书馆等的运作情况,进行了中美门户网站模式的比较。进而进行了中美数字图书馆电子商务发展比较。 相似文献
14.
Morris SC Moskowitz PD Sevian WA Silberstein S Hamilton LD 《Science (New York, N.Y.)》1979,206(4419):654-662
Several technologies to convert coal to liquid and gaseous fuels are being developed in the United States, some with support from the Department of Energy. Substitution of these technologies for those currently being used will produce different health and environmental hazards. In this article, selected health and environmental effects of four coal conversion and four existing technologies are compared. For each technology, the emission estimates for complete fuel cycles, including all steps in fuel use from extraction to the end use of space and water heating by electricity or direct combustion, were prepared by means of the Brookhaven Energy System Network Simulator model. Quantitative occupational health and safety estimates are presented for the extraction, transportation, distribution, processing, and conversion activities associated with each technology; also included are some public health damage estimates arising from fuel transportation and air pollution impacts. Qualitative estimates of health damage due to polycyclic organic matter and reduced sulfur are discussed. In general, energy inefficiencies, environmental residuals, and hence implied environmental effects and health damage increase in the order: (i) direct combustion of natural gas and oil, (ii) direct combustion of synthetic gas and oil, (iii) central-station electric power produced from synthetic gas, (iv) central-station electric power produced from coal, and (v) central-station electric power produced by the combustion of synthetic liquid fuels. The compliance and conflict of these technologies with the amendments of the Clean Air Act and other legislation are discussed. 相似文献
15.
Tillman JE 《Science (New York, N.Y.)》1980,210(4470):595-600
A geothermal resource that consists of hot water at moderate temperatures (below 125 degrees C) underlies many areas in the central and eastern United States. Programs funded by the Department of Energy have revealed that this resource is definable and economically competitive with conventional fuels for use in direct heat applications. The resource, therefore, has the potential for reducing our dependence on the imported oil used for space heating. However, front-end costs and risks to explore, drill, test, and evaluate the magnitude of the resource have inhibited development. The question is, therefore, how much federal stimulation will be needed to convince private capital to exploit this widespread low-quality energy source. 相似文献
16.
基于对生态农业特征及国外生态农业发展成功经验的分析,比较美国和中国生态农业发展现状、模式和经验,结合中国农业实践,提出了中国生态农业发展模式和对策。 相似文献
17.
基于大量一手文献的翻译、整理，从公共体育、专业体育和课外体育三个方面，阐述美国大学体育
的创建历程。在此基础上，从合理性、合法性层面，揭示美国大学体育构建的内部机制。体育思想的转变
为美国大学体育的萌生提供了动力来源，并通过合理性、合法性的构建指引、规约了美国大学体育体系的
构建；由此得到的启示是大学体育改革和发展必须有先进的体育思想为基础、以完善的制度为保障。 相似文献
18.
Number of siblings and educational attainment 总被引：1，自引：0，他引：1
J Blake 《Science (New York, N.Y.)》1989,245(4913):32-36
Family background continues to be closely related to individuals' educational attainment in the United States. A notable change in one aspect of this background, number of siblings, is occurring as fertility is becoming extremely low. Examination of the negative relation between individuals' sibling number and years of schooling indicates that education among those with many siblings is disproportionately cut short before high school graduation. Because there is a strong negative relation between number of siblings and scores on tests measuring verbal ability, recent reductions in sibling number would be expected to contribute to enhanced verbal ability and increasing years of schooling for those born now in the United States. 相似文献
19.
Macneil JS 《Science (New York, N.Y.)》2000,289(5484):1448b-1449b
Forest fires burning in the western United States have already scorched over 2.5 million hectares this summer. Now a federal proposal to prevent them by paying loggers to cut smaller trees is generating heat among ecologists, who say the approach may not be right for all forests--or all fires. 相似文献
20.
The geographic and temporal variability of freshwater supply in the United States constrains the choice and level of use of future energy sources. Ecological criteria for acceptable freshwater consumption, together with hydrological data on stream flow, provide a framework for estimating these constraints. The water consumption requirements for a variety of energy options are presented, and comparative judgments drawn. Attention is focused on problems resulting from synthetic, gaseous, and liquid fuel production. Scenarios describing possible future levels of coal and electricity use are analyzed. They point to the importance of water supply constraints in both the eastern and western United States. 相似文献